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Immobilized Metal Ion Interaction 19
Table 1
Immobthzed Chelating Groups and Metal Ions Used
for Immobilized Metal Ion Allinity Chromatography
Suitable Commercial
Chelatmg group metal ions Reference source
Immodiacetate
2-Hydroxy-3 [ N (2-
pyrtdylmethyl)
glycme]propyl
crAlky1 mtrilo
triacetic acid
Carboxymethylated
asparhc acid
Tris (carboxy-
methyl) ethylene
diamme
(GHHPH) nG*
Transitional
Transrnonal
192
3
Pharmacia LKB
Pierce
Sigma
Boehrmger
Mannhelm
TosoHaas
Not available
Transitional 4 Not avalable
ww 13 Not available
Transittonal 2 Not available
Transinonal 14,15 Not available
*Letters represent standard l-letter amino acid codes (C = glycme, H =
buudme, P = prolme) The number of internal repeat units IS given by n (n = 1,2,
3, and 5)
metal chelating group with a lower affinity for proteins (222). An
important contribution to the correct use of IMAC for protein purifi-
cation is a simplified presentation of the various sample elution proce-
dures. This is especially important to the first-time user. There are
many ways to decrease the interaction between an immobiltzed metal
ion and the adsorbed protein. Two of these methods are effkient and
easily controlled; they will be presented in detail in this chapter. Inter-
pretation of MAC results for purposes other than separation (i.e.,
analysis of surface topography and metal ion transfer) has been dis-
cussed elsewhere and is beyond the scope of this contribution.
2. Materials
The following list of materials and reagents is only representative.
Other stationary phases, metal ions, affinity reagents, and mobile phase
modifiers are used routinely.